Feed Question: Starter vs. Broiler

Cornish X newbie here. Have been feeding New Country Organics. Feed store gave my husband a bag of Starter at 21% instead of the Broiler at 19%. Is it ok to use or should I take it back? They are 5.5 weeks old now and we'd go through the bag in about a week. I'm seeing folks using much higher protein here with success, so hoping is ok to use up a bag of Starter? I had just switched them from Starter to Broiler about a week ago. Thanks!